This invention concerns a miniature pushbutton for an electronic timepiece and comprises a socket having an innermost extremity terminating in a base portion provided with an opening and a head-stem member integrally formed by a first portion adapted to pass through said opening and a second portion adapted to slide freely in the socket, said second portion including a groove arranged to retain sealing means cooperating with the interior wall of the socket.
Swiss published patent application No. 5 582/74 shows a similar arrangement to that descrived above. A head and a flange between which is placed a toroidal seal form a second portion of the stem which cooperates with a socket force fitted or glued into the case band of the timepiece. The first portion of the stem passes through an opening provided in the base portion of the socket. This first stem portion presents a second flange obtained by a setting operation and intended to retain the stem in the socket against the force of a spring. This arrangement presents at least two disadvantages. Initially the return spring incorporated into the pushbutton takes up considerable space both in length and in diameter and is thus not suitable for the obtaining of a miniature pushbutton. Additionally the setting operation on the stem renders dissassembly impossible which may hinder the operation of assembling and dissassembling the watch.
A solution for overcoming this latter disadvantage has already been suggested in Swiss Pat. No. 303 715. Here, and as may often be the case, the movement is of smaller diameter than the case-band in which it is arranged and its dial being supported on an interior shoulder of the case band-bezel oversteps this movement. In such case the first portion of the stem of the pushbutton after having passed through the opening at the base of the socket provides only a small projection at the interior of the case. The junction between the second portion of the stem and the member to be actuated on the movement is obtained by an extension which is assembled after the movement has been set into the case. If an enlarging cage or circle is employed in order to adjust a small movement to a case of larger diameter, such junction may be realized by piercing a hole in the circle or cage and introducing therein an extension. In addition to the fact that this patent does not provide a solution to the miniaturization of the pushbutton (since a return spring is always necessary), it entails the difficulty of a complicated construction obliging the utilization of additional parts and renders more difficult the operations of assembly and dissassembly of the timepiece.
It is becoming more and more common to provide timepieces of greatly reduced dimensions, above all in respect of the thickness thereof. In such a case one has available very little space in the thickness as represented by the case-band and the pushbutton corrector must be on the scale of the timepiece in which it is mounted, that is to say it must also be of very small dimensions. After a certain miniaturization has been realized it is no longer possible to provide a return spring forming an integral portion of the pushbutton since the force available therefrom would be incapable of returning the head to its initial position prior to actuation. In such a timepiece it is equally desirable to reduce to the extent possible the number of mechanical parts in order to lower the cost and as well as to facilitate assembly. The means described in the cited patent and patent application do not permit achieving the objects of this invention which are the miniaturization of the pushbutton through elimination of its return spring, easy assembly of the said pushbutton by introduction of its stem from the exterior of the case and security of operation by a system preventing the stem from inadvertent separation from the socket in which it is mounted.
These object are attained by means of the construction as claimed.